Thanks to this, there is a nice tool to allow creating of yUML diagrams from the command line or scripts.
For example:
$ echo "[Hello]->[Tobin]" | yuml -s scruffy -o diagram.png
$ open diagram.png
Which opens this
To install this cool tool on your Mac, just do this:
$ sudo easy_install pip
$ sudo pip install https://github.com/wandernauta/yuml/zipball/master
That's it, you're DONE!